Er3+/Yb3+-codoped oxyfluoride crystallite glass was prepared with melting technique. The compositions and the melting temperature and the annealing temperature of the rare earth-doped crystallite glass were studied in...Er3+/Yb3+-codoped oxyfluoride crystallite glass was prepared with melting technique. The compositions and the melting temperature and the annealing temperature of the rare earth-doped crystallite glass were studied in detail. The emission spectra of samples were measured with the Hitachi F-4500 fluorescent photometer pumped by 980 nm wavelength laser. The up-conversion luminescence mechanism was illuminated on the view of the photophysics. By measuring the relationship between luminescent intensity and pump power, it is confirmed that the emission peaks at 550 nm belong to two-photon process, while that at 665 nm belongs to three-photon process. Moreover, the distributions of crystalline were determined by SEM.展开更多
Er^(3+)-doped heavy metal oxyfluoride silicate glass was fabricated and characterized, and the absorption spectrum and fluorescence spectrum of the glass were studied. The Judd-Ofelt intensity parameters Ω_t (t =2, ...Er^(3+)-doped heavy metal oxyfluoride silicate glass was fabricated and characterized, and the absorption spectrum and fluorescence spectrum of the glass were studied. The Judd-Ofelt intensity parameters Ω_t (t =2, 4, 6), spontaneous transition probability, fluorescence branching ratio and radiative lifetime of each energy levels for Er^(3+) were calculated by Judd-Ofelt theory, and stimulated emission cross-section of (()~4I_(13/2))→(()~4I_(15/2)) transition was calculated by McCumber theory. The results show that fluorescence full width at half maximum and stimulated emission cross-section of Er^(3+)-doped heavy metal oxyfluoride silicate glass are broad and large, respectively. Compared with other host glasses, the gain bandwidth property of Er^(3+)-doped heavy metal oxyfluoride silicate glass is close to those of tellurite and bismuth glasses, and has advantage over those of silicate, phosphate and germante glasses.展开更多
Novel oxyfluoride glasses are developed with the composition of 30SiO2-15Al2O3-28PbF2-22CdF2-0.1TmF3 - xYbF3 - (4.9 - x) AlF3(x=0, 0.5, 1.0, 1.5, 2.0) in tool fraction, Furthermore, the upconversion luminescence c...Novel oxyfluoride glasses are developed with the composition of 30SiO2-15Al2O3-28PbF2-22CdF2-0.1TmF3 - xYbF3 - (4.9 - x) AlF3(x=0, 0.5, 1.0, 1.5, 2.0) in tool fraction, Furthermore, the upconversion luminescence characteristics under a 970nm excitation are investigated. Intense blue, red and near infrared luminescences peaked at 453nm, 476nm, 647nm and 789nm, which correspond to the transitions of Tm^3+: ^1D2 →^3F4, ^1G4 →^3H6, ^1G4 →^3F4, and ^3H4 →^3H6, respectively, are observed. Due to the sensitization of Yb^3+ ions, all the upconversion luminescence intensities are enhanced considerably with Yb^3+ concentration increasing. The upconversion mechanisms are discussed based on the energy matching rule and quadratic dependence on excitation power. The results indicate that the dominant mechanism is the excited state absorption for those upconversion emissions.展开更多
The distribution characteristics of Er^3+ ions doped in the oxyfluoride glass ceramics containing LaF3 nanocrystals heat-treated at 650 ℃ for different durations were investigated. The results of the integral absor...The distribution characteristics of Er^3+ ions doped in the oxyfluoride glass ceramics containing LaF3 nanocrystals heat-treated at 650 ℃ for different durations were investigated. The results of the integral absorption cross-section analysis demonstrated that the partition fraction of Er^3+ in LaF3 nanocrystals increases with prolonging of heating time, The anomalous phenomena of Er^3+ emissions in the up-and the down-conversion fluorescence spectra are well explained based on the calculated results.展开更多
The Pr3+-Yb3+ co-doped oxyfluoride glass-ceramics containing CaF2 nanocrystals were obtained by thermal treatment on the as-made glasses. The structure of fluoride nanocrystals was investigated. The light-emitting m...The Pr3+-Yb3+ co-doped oxyfluoride glass-ceramics containing CaF2 nanocrystals were obtained by thermal treatment on the as-made glasses. The structure of fluoride nanocrystals was investigated. The light-emitting mechanism of pr3+-yb3+ in the near infrared region was proposed and the fluorescence lifetime and quantum efficiency was calculated. The results indicate that the main phase in the oxyfluoride glass- ceramics is CaF2 nanocrystal sized at 30 nm. Energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) have proved the incorporation of Pr3+ and Yb3+ into CaF2 nanocrystal lattice, Near-infrared quantum cutting involving Yb3+ 980 nm and 1 015 tun (2F5/2→2F7/2) emission has been achieved upon the excitation of the 3P0 energy level of Pr3+ at 482 nm. The fluorescence lifetime decreases sharply and quantum efficiency increases with increasing Yb3+ concentration, and the optimal quantum efficiency reaches 191%.展开更多
A series of new binary rare earth oxyfluoride (Sm2O3-LaF3) catalysts have been developed for ODE reaction. High C2H4 selectivity(91.5%) with C2H6 conversion 21.7% was achieved on the catalyst Sm2O3/LaF3 with molar rat...A series of new binary rare earth oxyfluoride (Sm2O3-LaF3) catalysts have been developed for ODE reaction. High C2H4 selectivity(91.5%) with C2H6 conversion 21.7% was achieved on the catalyst Sm2O3/LaF3 with molar ratio 1/1 at 700℃. The addition of 16.7 mol% BaF2 into Sm2O3/LaF3(1/1 in mol) led to the increase of C2H6 conversion from 21.7% to 40.8%,however. the change of ethene seletivity was not apparent (from 91.5% to 88.0%).展开更多
A series of oxyfluoride glasses with the compositions of 75 mol% TeO2, 10 mol% Nb2O5, (15 mol%-x) BaO, x BaF2 (x =0 mol%, 5 mol%, 10 mol%, 15 mol%) doped with Yb2O3 were prepared by the melt-quenching method. Thei...A series of oxyfluoride glasses with the compositions of 75 mol% TeO2, 10 mol% Nb2O5, (15 mol%-x) BaO, x BaF2 (x =0 mol%, 5 mol%, 10 mol%, 15 mol%) doped with Yb2O3 were prepared by the melt-quenching method. Their emission cross-sections, fluorescence lifetimes, and gain properties were investigated by using the absorption spectra and the fluorescence decay curves. The results show that by substituting BaF2 for BaO, the emission cross-section decreases from 1.37 pm^2 to 1.21 pm^2, and the fluorescence lifetime increases from 0.71 ms to 0.96 ms. These properties indicate that this oxyfluoride tellurite glass may have potential uses as the Yb2O3-doped gain medium in a solid laser.展开更多
Divalent metal fluorides MF2 (M=Sr, Mg, Ca) in oxyfluoride tellurite glasses TeO2-BaF2-LaF3 were synthesized. The densities, refractive indices and characteristic temperatures of synthesized glasses were measured. T...Divalent metal fluorides MF2 (M=Sr, Mg, Ca) in oxyfluoride tellurite glasses TeO2-BaF2-LaF3 were synthesized. The densities, refractive indices and characteristic temperatures of synthesized glasses were measured. The influence of divalent metal fluorides-MF2(M=Sr, Mg, Ca) on the thermal stability of oxyfluoride tellurite glasses TeO2-BaF2-LaF3 were studied. Results show that the replacement of BaF2 by SrF2 and MgF2 can enhance the thermal stability against crystallization of the glass. A glass system with good thermal stability was produced, which could be a potential candidate for the host materials of the fiber devices.展开更多
The MOC reaction over ZrO_2/LaF_3, CeO_2/LaF_3 and ThO_2/LaF_3 catalysts indicated that these catalysts had high activity and high C_2 selectivity at low temperature. In the temperature range 480℃ to 650℃. The metha...The MOC reaction over ZrO_2/LaF_3, CeO_2/LaF_3 and ThO_2/LaF_3 catalysts indicated that these catalysts had high activity and high C_2 selectivity at low temperature. In the temperature range 480℃ to 650℃. The methane conversion was 24. 4% to 30. 8% and the C_2 selectivity was 40. 0% to 55. 4%. The XRD characterization of the catalysts indicated that O^2. and F exchang happened and LaOF was formed.展开更多
Two isostructural inorganic-organic hybrid M(II)–Nb(V) oxyfluorides, namely, M(H2O)2(pyz)NbOF5 (M=Co 1, Cu 2; pyz=pyrazine) have been hydrothermally synthesized and structurally characterized. Both compound...Two isostructural inorganic-organic hybrid M(II)–Nb(V) oxyfluorides, namely, M(H2O)2(pyz)NbOF5 (M=Co 1, Cu 2; pyz=pyrazine) have been hydrothermally synthesized and structurally characterized. Both compounds possess two-dimensional layer structure constructed by neutral M(H2O)2NbOF5 chains inter-connected via bridging pyrazine ligands. The structure is further extended into three-dimensional supramolecular architecture through inter-layer H-bonding interactions between the coordinated water molecules and fluorine ions. The luminescent properties and thermal stability of both compounds have been investigated.展开更多
Pr^(3+)-doped transparent oxyfluoride glass-ceramic containing tetragonal LiYF_4 nanocrystals has been synthesized by melting-quenching method and subsequent thermal treatment and spectroscopic properties of Pr^(...Pr^(3+)-doped transparent oxyfluoride glass-ceramic containing tetragonal LiYF_4 nanocrystals has been synthesized by melting-quenching method and subsequent thermal treatment and spectroscopic properties of Pr^(3+) ions were investigated. The crystalline phase and microstructure of the LiYF_4 nanocrystals were studied by X-ray diffraction(XRD) and transmission electron microscopy(TEM), respectively. Compared with those of Pr^(3+)-doped glass(Pr^(3+):PG), the sharp absorption and emission bands of Pr^(3+)-doped glass-ceramic(Pr^(3+):GC) reveal parts of Pr^(3+) ions are incorporated into LiYF_4 nanocrystals. The peak absorption cross-section at 443 nm(~3H_4 → ~3P_2) adds to 110% and the full width at half maximum(FWHM) for the band around 443 nm reduces from 22 to 14 nm after crystallization. The fluorescence lifetime of the ~3P_0 multiplet of Pr^(3+) ions increases from 5.35 to 11.14 μs after crystallization. The results indicate that this glass-ceramic is promising to be a visible laser material.展开更多
A systematic investigation on fluorescence spectroscopy of trivalent thulium doped in oxyfluoride glass ceramics containing LaF3 nanocrystals has been carried out in a spectral range from 400 to 900 nm under the direc...A systematic investigation on fluorescence spectroscopy of trivalent thulium doped in oxyfluoride glass ceramics containing LaF3 nanocrystals has been carried out in a spectral range from 400 to 900 nm under the direct excitation of 1D2 level at a low temperature. Specific optical transitions related to the fluorescence emissions are studied based on experimental measurements in frequency and time domain. Fluorescence emissions from the ions in crystal phase are distinguished from what in glass phase and their spectroscopic properties are explored. The dynamical process shows that the temporal decay of fluorescence emission consists of two parts: a rapid decay from the ions in glass phase and a slower decay from the ions in crystal phase.展开更多
It is interesting to explore a novel oxyfluoride glass with good glass stability to be applied in optical communication and optical windows at infrared(IR)wavelength.We demonstrated a new glass of Ga_(2)O_(3)-doped Zr...It is interesting to explore a novel oxyfluoride glass with good glass stability to be applied in optical communication and optical windows at infrared(IR)wavelength.We demonstrated a new glass of Ga_(2)O_(3)-doped ZrF_(4)-BaF_(2)-LaF_(3)-AlF_(3)-NaF(ZBLAN)glass using a melt-quenched technique.The effect of Ga_(2)O_(3)-doping on glass properties and structure was characterized by differential thermal analysis(DTA),IR spectra,Raman spectra,and X-ray diffraction(XRD).It is found that the glass thermal stability(ΔT)increases by 14% when the addition of Ga_(2)O_(3) reaches 1mol%.With the increase of Ga_(2)O_(3) content,the density and refractive index of the glasses increase.Ga_(2)O_(3)-doping does not affect the IR cut-off edge and maintains the transmittance near 90% in the range of 2.5-5μm,which is almost equal to the undoped sample.Ga_(2)O_(3)-doping hardly changes the initial coordinated structure of Zr^(4+)according to the results of IR spectra and Raman spectra.Ga^(3+)holds in the interstice site of the network coordinated with F^(-)and the part of O_(2)-introduced by Ga_(2)O_(3) is coordinated with Al^(3+)forming Al-O bond.This study offers a new glass composition that may be potentially used in fabricating mid-IR optical fiber and large-size glasses for IR windows.展开更多
The infrared quantum cutting of oxyfluoride nanophase vitroceramics Tb(0.7)Yb(3):FOV has been studied in the present paper. The actual quantum cutting efficiency formula calculated from integral fluorescence inte...The infrared quantum cutting of oxyfluoride nanophase vitroceramics Tb(0.7)Yb(3):FOV has been studied in the present paper. The actual quantum cutting efficiency formula calculated from integral fluorescence intensity is extended to the case of Tb(0.7)Yb(3):FOV. The visible and the infrared fluorescence spectra and their integral fluorescence intensities are measured from static fluorescence experiment. Lifetime curve is measured from dynamic fluorescence experiment. It is found that the total actual quantum cutting efficiency n of the excited 5D4 level is about 93.7%, and that of excited (5D3, 5G6) levels is 93.5%. It is also found that the total theoretical quantum cutting efficiency upper limit ?~x^Yb of the 485.5 nm excited 5D4 level is about 121.7%, and that of 378.5 nm excited (5D3, 5G6) levels is 137.2%.展开更多
Oxyfluoride borosilicate glass with the molar composition of 60SiO2-15B2O3- 15Na2O-8CaF2-2NaF-0.25Eu2O3 was synthesized lay a traditional glass melting method. Glass ceramics containing CaF2 nanocrystals were prepared...Oxyfluoride borosilicate glass with the molar composition of 60SiO2-15B2O3- 15Na2O-8CaF2-2NaF-0.25Eu2O3 was synthesized lay a traditional glass melting method. Glass ceramics containing CaF2 nanocrystals were prepared by heat treating the glass samples at a temperature in the range of 6204580 ℃. The results of X-ray diffraction (XRD) indicated that the average crystallite size and the lattice constant of CaF2 nanocrystals increased with the heat treatment temperature increasing. The luminescence spectra showed that the emission intensity of Eu3+ doped glass ceramics was stronger than that of the glass matrix, and increased with the heat treatment temperature increasing. The left edge of excitation band shifted to shorter wavelength in the glass ceramics. The local environments of Eu3+ ions in the glass and glass ceramics were different.展开更多
Rare earth ion-doped fluorescent glass has become a hotspot due to its characteristics.This work shows that the prepared Dy^3+and Dy^3+/Eu^3+doped glasses have white light emission under ultraviolet excitation.There i...Rare earth ion-doped fluorescent glass has become a hotspot due to its characteristics.This work shows that the prepared Dy^3+and Dy^3+/Eu^3+doped glasses have white light emission under ultraviolet excitation.There is a higher yellow light/blue light(Y/B)value,indicating an increase in the covalentity of Dy-O,and decrease in the symmetry with the increasing concentration of dopants(Dy^3+).The correlated color temperature(CCT)can be effectively reduced by the red light emission of Eu^3+,and the order of influence of excitation wavelength on CCT is 395 nm>382 nm>365 nm.The delay curve demonstrates the energy transfer from Dy^3+to Eu^3+.The glass has the characteristics of anti-blue light damage and wide tunable color temperature,which illustrates that it has potential application in the field of white LED.展开更多
The transparent oxyfluoride glass ceramics containing Ba Gd F5 nanocrystals were prepared with a composition of 42 Si O2-12Na2O-16Al2O3-24 Ba F2-4Gd2O3-2Ce F3(mol.%) by thermal treatment technology. The typical DSC ...The transparent oxyfluoride glass ceramics containing Ba Gd F5 nanocrystals were prepared with a composition of 42 Si O2-12Na2O-16Al2O3-24 Ba F2-4Gd2O3-2Ce F3(mol.%) by thermal treatment technology. The typical DSC curve, X-ray diffraction(XRD) and transmission electron microscopy(TEM) patterns were measured. The transmission spectra and luminescent properties were investigated. The decay times of the Gd^3+ ions at 312 nm excited with 275 nm for the Ce^3+ ions doped glass and glass ceramics specimens and the energy transfer process between Gd^3+ ions and Ce^3+ ions were also studied. The XRD analysis and the TEM images confirmed the generation of the spherical Ba Gd F5 nanocrystals. Compared with the PG specimen, the intensity of the luminescence spectra of the glass ceramics specimens was apparently enhanced with the heat treatment temperature increasing, and a blue shift in the excitation spectra and the emission spectra of glass ceramics specimens was obviously observed. In the fluorescence decay curves of the Gd^3+ ions, it could be obviously observed that the fluorescent intensity decays in the Ce^3+ ions doped glass and glass ceramics specimens decreased rapidly with the increase of the heat treatment temperature. In addition, the energy transfer efficiency from Gd3+ions to Ce^3+ ions was also calculated.展开更多
The ultraviolet upconversion luminescence of Tm3+ ions sensitized by Yb3+ ions in oxyfluoride nanophase vitroceramics when excited by a 975 nm diode laser was studied. An ultraviolet upconversion luminescence line pos...The ultraviolet upconversion luminescence of Tm3+ ions sensitized by Yb3+ ions in oxyfluoride nanophase vitroceramics when excited by a 975 nm diode laser was studied. An ultraviolet upconversion luminescence line positioned at 363.6 nm was found. It was attributed to the fluorescence transition of 1D2→3H6 of Tm3+ ion. Sev- eral visible upconversion luminescence lines at 450.7 nm, (477.0 nm, 462.5 nm), 648.5 nm, (680.5 nm, 699.5 nm) and (777.2 nm, 800.7 nm) were also found, which result respectively from the fluorescence transitions of 1D2→3F4, 1G4→3H6, 1G4→3F4, 3F3→3H6 and 3H4→3H6 of Tm3+ ion. The careful measurement and analysis of the variation of upconversion luminescence intensity F as a function of the 975 nm pumping laser power P prove that the upconversion luminescence of 1D2 state is partly a five-photon upconversion luminescence, and the upconversion lumines- cence of 1G4 state and 3H4 state are respectively the three-photon and two-photon upconversion luminescence. The theoretical analysis suggested that the upcon- version mechanism of the 363.6 nm 1D2→3H6 upconversion luminescence is partly the cross energy transfer of {3H4(Tm3+)→3F4(Tm3+), 1G4(Tm3+)→1D2(Tm3+)} and {1G4(Tm3+)→3F4(Tm3+), 3H4(Tm3+)→1D2(Tm3+)} between Tm3+ ions. In addition, the upconversion luminescence of 1G4 and 3H4 state results respectively from the se- quential energy transfer {2F5/2(Yb3+)→2F7/2(Yb3+), 3H4(Tm3+)→1G4(Tm3+)} and {2F5/2(Yb3+) →2F7/2(Yb3+), 3F4(Tm3+)→3F2(Tm3+)} from Yb3+ ions to Tm3+ ions.展开更多
The upconversion luminescence of Er^3+/Yb^3+ ions is researched in a novel transparent oxyfluoride borosil- icate glass and glass ceramics under 980-nm excitation. Fluoride nanocrystals Ba2YF7 are successfully preci...The upconversion luminescence of Er^3+/Yb^3+ ions is researched in a novel transparent oxyfluoride borosil- icate glass and glass ceramics under 980-nm excitation. Fluoride nanocrystals Ba2YF7 are successfully precipitated in glass matrix, which is affirmed by the X-ray diffraction results. Compared with the parent glasses, significant enhancement of upconversion luminescence is observed in the Er^3+/Yb^3+ codoped transparent glass-ceramics, which may be due to the variation of coordination environment around Er^3+ and Yb^3+ ions after crystallization. The possible upconversion mechanism is also discussed.展开更多
Spectroscopic properties of Er3+/Yb3+-doped transparent oxyfluoride borosilicate glass ceramics containing YOF nanocrystals were systematically investigated. X-ray diffraction (XRD) confirmed the formation of YOF ...Spectroscopic properties of Er3+/Yb3+-doped transparent oxyfluoride borosilicate glass ceramics containing YOF nanocrystals were systematically investigated. X-ray diffraction (XRD) confirmed the formation of YOF nanocrystals in the glassy matrix. Based on the Judd-Ofelt theory, the intensity parameters Ωi (i=2, 4, 6), spontaneous emission probability, radiative lifetime, radiative quantum efficiency and the effective emission bandwidth were investigated. The upconversion luminescence intensity of Er3+ ions in the glass ceramics increased significantly with the increasing crystallization temperature. The transition mechanisms of the green and red upconversion luminescence were ascribed to a two-photon process, and the blue upconversion luminescence was a three-photon absorption process.展开更多
文摘Er3+/Yb3+-codoped oxyfluoride crystallite glass was prepared with melting technique. The compositions and the melting temperature and the annealing temperature of the rare earth-doped crystallite glass were studied in detail. The emission spectra of samples were measured with the Hitachi F-4500 fluorescent photometer pumped by 980 nm wavelength laser. The up-conversion luminescence mechanism was illuminated on the view of the photophysics. By measuring the relationship between luminescent intensity and pump power, it is confirmed that the emission peaks at 550 nm belong to two-photon process, while that at 665 nm belongs to three-photon process. Moreover, the distributions of crystalline were determined by SEM.
文摘Er^(3+)-doped heavy metal oxyfluoride silicate glass was fabricated and characterized, and the absorption spectrum and fluorescence spectrum of the glass were studied. The Judd-Ofelt intensity parameters Ω_t (t =2, 4, 6), spontaneous transition probability, fluorescence branching ratio and radiative lifetime of each energy levels for Er^(3+) were calculated by Judd-Ofelt theory, and stimulated emission cross-section of (()~4I_(13/2))→(()~4I_(15/2)) transition was calculated by McCumber theory. The results show that fluorescence full width at half maximum and stimulated emission cross-section of Er^(3+)-doped heavy metal oxyfluoride silicate glass are broad and large, respectively. Compared with other host glasses, the gain bandwidth property of Er^(3+)-doped heavy metal oxyfluoride silicate glass is close to those of tellurite and bismuth glasses, and has advantage over those of silicate, phosphate and germante glasses.
基金Project supported by the Shanghai "Post-Qi-Ming-Xing plan" for Young Scientists, China (Grant No 04QMX1448) and the National Natural Science Foundation of China (Grant No 60207006).The author would like to thank Wen L,Shen Y H and Zhao Y for their help in machining and measuring.
文摘Novel oxyfluoride glasses are developed with the composition of 30SiO2-15Al2O3-28PbF2-22CdF2-0.1TmF3 - xYbF3 - (4.9 - x) AlF3(x=0, 0.5, 1.0, 1.5, 2.0) in tool fraction, Furthermore, the upconversion luminescence characteristics under a 970nm excitation are investigated. Intense blue, red and near infrared luminescences peaked at 453nm, 476nm, 647nm and 789nm, which correspond to the transitions of Tm^3+: ^1D2 →^3F4, ^1G4 →^3H6, ^1G4 →^3F4, and ^3H4 →^3H6, respectively, are observed. Due to the sensitization of Yb^3+ ions, all the upconversion luminescence intensities are enhanced considerably with Yb^3+ concentration increasing. The upconversion mechanisms are discussed based on the energy matching rule and quadratic dependence on excitation power. The results indicate that the dominant mechanism is the excited state absorption for those upconversion emissions.
基金the National Natural Science Foundation of China (No. 50672098)the Project of Nano-molecular Functional Materials of Fujian Province (2005HZ01-1)
文摘The distribution characteristics of Er^3+ ions doped in the oxyfluoride glass ceramics containing LaF3 nanocrystals heat-treated at 650 ℃ for different durations were investigated. The results of the integral absorption cross-section analysis demonstrated that the partition fraction of Er^3+ in LaF3 nanocrystals increases with prolonging of heating time, The anomalous phenomena of Er^3+ emissions in the up-and the down-conversion fluorescence spectra are well explained based on the calculated results.
基金Funded by Key Laboratory for Ultrafine Materials of Ministry of Education(No.08DZ2230500),School of Materials Science and Engineering,East China University of Science and Technology
文摘The Pr3+-Yb3+ co-doped oxyfluoride glass-ceramics containing CaF2 nanocrystals were obtained by thermal treatment on the as-made glasses. The structure of fluoride nanocrystals was investigated. The light-emitting mechanism of pr3+-yb3+ in the near infrared region was proposed and the fluorescence lifetime and quantum efficiency was calculated. The results indicate that the main phase in the oxyfluoride glass- ceramics is CaF2 nanocrystal sized at 30 nm. Energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) have proved the incorporation of Pr3+ and Yb3+ into CaF2 nanocrystal lattice, Near-infrared quantum cutting involving Yb3+ 980 nm and 1 015 tun (2F5/2→2F7/2) emission has been achieved upon the excitation of the 3P0 energy level of Pr3+ at 482 nm. The fluorescence lifetime decreases sharply and quantum efficiency increases with increasing Yb3+ concentration, and the optimal quantum efficiency reaches 191%.
文摘A series of new binary rare earth oxyfluoride (Sm2O3-LaF3) catalysts have been developed for ODE reaction. High C2H4 selectivity(91.5%) with C2H6 conversion 21.7% was achieved on the catalyst Sm2O3/LaF3 with molar ratio 1/1 at 700℃. The addition of 16.7 mol% BaF2 into Sm2O3/LaF3(1/1 in mol) led to the increase of C2H6 conversion from 21.7% to 40.8%,however. the change of ethene seletivity was not apparent (from 91.5% to 88.0%).
基金supported by the National Natural Science Foundation of China(Grant Nos.61177086,61307046,and 61308086)the West Light Foundation of the Chinese Academy of Sciences(Grant No.Y129261213)
文摘A series of oxyfluoride glasses with the compositions of 75 mol% TeO2, 10 mol% Nb2O5, (15 mol%-x) BaO, x BaF2 (x =0 mol%, 5 mol%, 10 mol%, 15 mol%) doped with Yb2O3 were prepared by the melt-quenching method. Their emission cross-sections, fluorescence lifetimes, and gain properties were investigated by using the absorption spectra and the fluorescence decay curves. The results show that by substituting BaF2 for BaO, the emission cross-section decreases from 1.37 pm^2 to 1.21 pm^2, and the fluorescence lifetime increases from 0.71 ms to 0.96 ms. These properties indicate that this oxyfluoride tellurite glass may have potential uses as the Yb2O3-doped gain medium in a solid laser.
基金the "Qimingxing" Project (No. 04QMX1448) of Shanghai Municipal Science and Technology Commission the National Natural Science Foundation of China (Grant No. 50572110).
文摘Divalent metal fluorides MF2 (M=Sr, Mg, Ca) in oxyfluoride tellurite glasses TeO2-BaF2-LaF3 were synthesized. The densities, refractive indices and characteristic temperatures of synthesized glasses were measured. The influence of divalent metal fluorides-MF2(M=Sr, Mg, Ca) on the thermal stability of oxyfluoride tellurite glasses TeO2-BaF2-LaF3 were studied. Results show that the replacement of BaF2 by SrF2 and MgF2 can enhance the thermal stability against crystallization of the glass. A glass system with good thermal stability was produced, which could be a potential candidate for the host materials of the fiber devices.
文摘The MOC reaction over ZrO_2/LaF_3, CeO_2/LaF_3 and ThO_2/LaF_3 catalysts indicated that these catalysts had high activity and high C_2 selectivity at low temperature. In the temperature range 480℃ to 650℃. The methane conversion was 24. 4% to 30. 8% and the C_2 selectivity was 40. 0% to 55. 4%. The XRD characterization of the catalysts indicated that O^2. and F exchang happened and LaOF was formed.
基金supported by the NNSFC (Nos. 20771102 and 20873149)NSF of Fujian Province (No. 2008J0174 )973 Program (No. 2006CB932904)
文摘Two isostructural inorganic-organic hybrid M(II)–Nb(V) oxyfluorides, namely, M(H2O)2(pyz)NbOF5 (M=Co 1, Cu 2; pyz=pyrazine) have been hydrothermally synthesized and structurally characterized. Both compounds possess two-dimensional layer structure constructed by neutral M(H2O)2NbOF5 chains inter-connected via bridging pyrazine ligands. The structure is further extended into three-dimensional supramolecular architecture through inter-layer H-bonding interactions between the coordinated water molecules and fluorine ions. The luminescent properties and thermal stability of both compounds have been investigated.
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB20000000)
文摘Pr^(3+)-doped transparent oxyfluoride glass-ceramic containing tetragonal LiYF_4 nanocrystals has been synthesized by melting-quenching method and subsequent thermal treatment and spectroscopic properties of Pr^(3+) ions were investigated. The crystalline phase and microstructure of the LiYF_4 nanocrystals were studied by X-ray diffraction(XRD) and transmission electron microscopy(TEM), respectively. Compared with those of Pr^(3+)-doped glass(Pr^(3+):PG), the sharp absorption and emission bands of Pr^(3+)-doped glass-ceramic(Pr^(3+):GC) reveal parts of Pr^(3+) ions are incorporated into LiYF_4 nanocrystals. The peak absorption cross-section at 443 nm(~3H_4 → ~3P_2) adds to 110% and the full width at half maximum(FWHM) for the band around 443 nm reduces from 22 to 14 nm after crystallization. The fluorescence lifetime of the ~3P_0 multiplet of Pr^(3+) ions increases from 5.35 to 11.14 μs after crystallization. The results indicate that this glass-ceramic is promising to be a visible laser material.
基金Project supported by the Foundation for Key Program of Ministry of Education, China (Grant No 108118)
文摘A systematic investigation on fluorescence spectroscopy of trivalent thulium doped in oxyfluoride glass ceramics containing LaF3 nanocrystals has been carried out in a spectral range from 400 to 900 nm under the direct excitation of 1D2 level at a low temperature. Specific optical transitions related to the fluorescence emissions are studied based on experimental measurements in frequency and time domain. Fluorescence emissions from the ions in crystal phase are distinguished from what in glass phase and their spectroscopic properties are explored. The dynamical process shows that the temporal decay of fluorescence emission consists of two parts: a rapid decay from the ions in glass phase and a slower decay from the ions in crystal phase.
基金Funded by the Natural Science Foundation of Shanghai(No.19YF1453300)the National Natural Science Foundation of China(Nos.52072122,51872092,and 52002385)。
文摘It is interesting to explore a novel oxyfluoride glass with good glass stability to be applied in optical communication and optical windows at infrared(IR)wavelength.We demonstrated a new glass of Ga_(2)O_(3)-doped ZrF_(4)-BaF_(2)-LaF_(3)-AlF_(3)-NaF(ZBLAN)glass using a melt-quenched technique.The effect of Ga_(2)O_(3)-doping on glass properties and structure was characterized by differential thermal analysis(DTA),IR spectra,Raman spectra,and X-ray diffraction(XRD).It is found that the glass thermal stability(ΔT)increases by 14% when the addition of Ga_(2)O_(3) reaches 1mol%.With the increase of Ga_(2)O_(3) content,the density and refractive index of the glasses increase.Ga_(2)O_(3)-doping does not affect the IR cut-off edge and maintains the transmittance near 90% in the range of 2.5-5μm,which is almost equal to the undoped sample.Ga_(2)O_(3)-doping hardly changes the initial coordinated structure of Zr^(4+)according to the results of IR spectra and Raman spectra.Ga^(3+)holds in the interstice site of the network coordinated with F^(-)and the part of O_(2)-introduced by Ga_(2)O_(3) is coordinated with Al^(3+)forming Al-O bond.This study offers a new glass composition that may be potentially used in fabricating mid-IR optical fiber and large-size glasses for IR windows.
基金supported by the National Natural Science Foundation of China (Grant No. 10674019)
文摘The infrared quantum cutting of oxyfluoride nanophase vitroceramics Tb(0.7)Yb(3):FOV has been studied in the present paper. The actual quantum cutting efficiency formula calculated from integral fluorescence intensity is extended to the case of Tb(0.7)Yb(3):FOV. The visible and the infrared fluorescence spectra and their integral fluorescence intensities are measured from static fluorescence experiment. Lifetime curve is measured from dynamic fluorescence experiment. It is found that the total actual quantum cutting efficiency n of the excited 5D4 level is about 93.7%, and that of excited (5D3, 5G6) levels is 93.5%. It is also found that the total theoretical quantum cutting efficiency upper limit ?~x^Yb of the 485.5 nm excited 5D4 level is about 121.7%, and that of 378.5 nm excited (5D3, 5G6) levels is 137.2%.
基金Project supported by Educational Department of Liaoning (L2011063)
文摘Oxyfluoride borosilicate glass with the molar composition of 60SiO2-15B2O3- 15Na2O-8CaF2-2NaF-0.25Eu2O3 was synthesized lay a traditional glass melting method. Glass ceramics containing CaF2 nanocrystals were prepared by heat treating the glass samples at a temperature in the range of 6204580 ℃. The results of X-ray diffraction (XRD) indicated that the average crystallite size and the lattice constant of CaF2 nanocrystals increased with the heat treatment temperature increasing. The luminescence spectra showed that the emission intensity of Eu3+ doped glass ceramics was stronger than that of the glass matrix, and increased with the heat treatment temperature increasing. The left edge of excitation band shifted to shorter wavelength in the glass ceramics. The local environments of Eu3+ ions in the glass and glass ceramics were different.
基金Project supported by Science and Technology Department of Jilin Province of China(20190302006GX)Technology Innovation Fund of Changchun University of Science and Technology(XJJLG-2017-06,XJJLG-2018-10)。
文摘Rare earth ion-doped fluorescent glass has become a hotspot due to its characteristics.This work shows that the prepared Dy^3+and Dy^3+/Eu^3+doped glasses have white light emission under ultraviolet excitation.There is a higher yellow light/blue light(Y/B)value,indicating an increase in the covalentity of Dy-O,and decrease in the symmetry with the increasing concentration of dopants(Dy^3+).The correlated color temperature(CCT)can be effectively reduced by the red light emission of Eu^3+,and the order of influence of excitation wavelength on CCT is 395 nm>382 nm>365 nm.The delay curve demonstrates the energy transfer from Dy^3+to Eu^3+.The glass has the characteristics of anti-blue light damage and wide tunable color temperature,which illustrates that it has potential application in the field of white LED.
基金supported by the National Natural Science Foundation of China(61275180,51472125)
文摘The transparent oxyfluoride glass ceramics containing Ba Gd F5 nanocrystals were prepared with a composition of 42 Si O2-12Na2O-16Al2O3-24 Ba F2-4Gd2O3-2Ce F3(mol.%) by thermal treatment technology. The typical DSC curve, X-ray diffraction(XRD) and transmission electron microscopy(TEM) patterns were measured. The transmission spectra and luminescent properties were investigated. The decay times of the Gd^3+ ions at 312 nm excited with 275 nm for the Ce^3+ ions doped glass and glass ceramics specimens and the energy transfer process between Gd^3+ ions and Ce^3+ ions were also studied. The XRD analysis and the TEM images confirmed the generation of the spherical Ba Gd F5 nanocrystals. Compared with the PG specimen, the intensity of the luminescence spectra of the glass ceramics specimens was apparently enhanced with the heat treatment temperature increasing, and a blue shift in the excitation spectra and the emission spectra of glass ceramics specimens was obviously observed. In the fluorescence decay curves of the Gd^3+ ions, it could be obviously observed that the fluorescent intensity decays in the Ce^3+ ions doped glass and glass ceramics specimens decreased rapidly with the increase of the heat treatment temperature. In addition, the energy transfer efficiency from Gd3+ions to Ce^3+ ions was also calculated.
基金the National Natural Science Foundation of China (Grant No. 10674019)
文摘The ultraviolet upconversion luminescence of Tm3+ ions sensitized by Yb3+ ions in oxyfluoride nanophase vitroceramics when excited by a 975 nm diode laser was studied. An ultraviolet upconversion luminescence line positioned at 363.6 nm was found. It was attributed to the fluorescence transition of 1D2→3H6 of Tm3+ ion. Sev- eral visible upconversion luminescence lines at 450.7 nm, (477.0 nm, 462.5 nm), 648.5 nm, (680.5 nm, 699.5 nm) and (777.2 nm, 800.7 nm) were also found, which result respectively from the fluorescence transitions of 1D2→3F4, 1G4→3H6, 1G4→3F4, 3F3→3H6 and 3H4→3H6 of Tm3+ ion. The careful measurement and analysis of the variation of upconversion luminescence intensity F as a function of the 975 nm pumping laser power P prove that the upconversion luminescence of 1D2 state is partly a five-photon upconversion luminescence, and the upconversion lumines- cence of 1G4 state and 3H4 state are respectively the three-photon and two-photon upconversion luminescence. The theoretical analysis suggested that the upcon- version mechanism of the 363.6 nm 1D2→3H6 upconversion luminescence is partly the cross energy transfer of {3H4(Tm3+)→3F4(Tm3+), 1G4(Tm3+)→1D2(Tm3+)} and {1G4(Tm3+)→3F4(Tm3+), 3H4(Tm3+)→1D2(Tm3+)} between Tm3+ ions. In addition, the upconversion luminescence of 1G4 and 3H4 state results respectively from the se- quential energy transfer {2F5/2(Yb3+)→2F7/2(Yb3+), 3H4(Tm3+)→1G4(Tm3+)} and {2F5/2(Yb3+) →2F7/2(Yb3+), 3F4(Tm3+)→3F2(Tm3+)} from Yb3+ ions to Tm3+ ions.
基金supported by the National Natural Science Foundation of China (Nos.60508014 and 50772102)the Program for New Century Excellent Talents in University (NCET-07-0786)+2 种基金the Science Technology Project of Zhejiang Province (No.2008C21162)the China Post-doctoral Science Foundation (No.20080430216)the Nature Science Foundation of Zhejiang Province(No.R406007)
文摘The upconversion luminescence of Er^3+/Yb^3+ ions is researched in a novel transparent oxyfluoride borosil- icate glass and glass ceramics under 980-nm excitation. Fluoride nanocrystals Ba2YF7 are successfully precipitated in glass matrix, which is affirmed by the X-ray diffraction results. Compared with the parent glasses, significant enhancement of upconversion luminescence is observed in the Er^3+/Yb^3+ codoped transparent glass-ceramics, which may be due to the variation of coordination environment around Er^3+ and Yb^3+ ions after crystallization. The possible upconversion mechanism is also discussed.
基金Project supported by National Science Foundation of China (51072190 and 11004177)Program for New Century Excellent Talents in University(NCET-07-0786)Zhejiang Provincial Natural Science Foundation of China (Z4100030 and Y4110621)
文摘Spectroscopic properties of Er3+/Yb3+-doped transparent oxyfluoride borosilicate glass ceramics containing YOF nanocrystals were systematically investigated. X-ray diffraction (XRD) confirmed the formation of YOF nanocrystals in the glassy matrix. Based on the Judd-Ofelt theory, the intensity parameters Ωi (i=2, 4, 6), spontaneous emission probability, radiative lifetime, radiative quantum efficiency and the effective emission bandwidth were investigated. The upconversion luminescence intensity of Er3+ ions in the glass ceramics increased significantly with the increasing crystallization temperature. The transition mechanisms of the green and red upconversion luminescence were ascribed to a two-photon process, and the blue upconversion luminescence was a three-photon absorption process.